Conventionally, magnetism has been measured to find a direction or the like. For example, an electronic compass measures a three-dimensional magnetic vector in order to find a precise direction. In this case, the electronic compass requires a magnetic sensor which individually measures magnetic vectors oriented in three directions of X, Y and Z.
A Hall element, an MR element or the like is employed as such a magnetic sensor. Nowadays, however, attention is focusing on a magneto-impedance element (appropriately abbreviated as an “MI element”), which is entirely different in structure and principle from such conventional elements and has an incomparably high sensitivity.
An MI element uses magneto-impedance effect (abbreviated as “MI effect”), which is a phenomenon in which when a high frequency pulse current or the like is applied to a magnetosensitive body such as an amorphous wire, its impedance changes with a magnetic field due to a skin effect. Magnetism such as an external magnetic field can be detected by measuring a change in its impedance or a change in magnetic flux generated in the magnetosensitive body and causing MI effect. It should be noted that a change in impedance is directly measured but a change in magnetic flux is measured by using a detection coil (a pickup coil) or the like wound around the magnetosensitive body. Such MI elements have already been used as MI sensors in electronic compasses or the like of a variety of devices.